Group III-V nitride semiconductors such as gallium nitride (GaN) and so on have been applied to develop semiconductor light emitting devices such as high brightness ultraviolet-blue and green light emitting diodes (LED: Light Emitting Diode) and bluish-purple-blue and green laser diodes (LD: Laser Diode) and so on.
In order to achieve high efficiency of LEDs, it is important to increase the crystallinity of GaN based semiconductors, and increase the internal quantum efficiency of the crystals. There is a large difference in lattice constants of InGaN which is used for the active layers of ultraviolet-blue and green LEDs, and GaN used for the substrate layers, so strain can easily occur, and efficiency can easily decrease due to piezo-polarization.
For example, technology is known that attempts to reduce the shift in the light emission peak wavelength and increase the brightness control range by adjusting the well layer density on a first GaN based compound semiconductor side and the well layer density on a second GaN based compound semiconductor side of an active layer.
There is still room for further improvement of the internal quantum efficiency.